1. Field of the Invention
The present invention relates to a cleaning liquid used in a process for forming a dual damascene structure and a method for treating a substrate therewith. The cleaning liquid of the invention is favorably used in production of a semiconductor device, such as IC and LSI.
2. Description of the Related Art
A semiconductor device, such as IC and LSI, is produced in the following process. A photoresist is uniformly coated on an electroconductive metallic film, an insulating film or a low dielectric material film formed on a substrate, such as a silicon wafer, by CVD vapor deposition process or the like. The photoresist is selectively subjected to exposure and development to form a photoresist pattern. The electroconductive metallic film, the insulating film or the low dielectric material film formed by CVD vapor deposition is selectively etched by using the photoresist pattern as a mask to form a minute circuit, and the photoresist layer thus becoming unnecessary is then removed with a remover liquid.
It is a trend in recent years that wiring circuits are becoming minute and multilayered as integration degree of semiconductor devices increases and chip size reduces, in which there arise problems in semiconductor devices, i.e., resistance of metallic films (wiring resistance) and wiring delay caused by wiring capacities. Accordingly, there are proposals of using metals, such as copper (Cu), having resistance smaller than that of aluminum (Al) having been mainly employed as a wiring material, and in recent years, two kinds of devices are being used, i.e., devices using an Al wiring (a metallic wiring using Al as a major component, such as Al and an Al alloy) and devices using a copper wiring (a metallic wiring using Cu as a major component).
Upon forming a Cu metallic wiring, in particular, a process is used in which a Cu multilayer wiring is formed without etching Cu by using a dual damascene process, owing to the low etching resistance of Cu. Various kinds of dual damascene processes have been proposed, an example of which will be described below, but the dual damascene process is not limited thereto.
After forming a Cu layer on a substrate, an interlayer film, such as a low dielectric film and an insulating film, is accumulated as being multilayered thereon, and a photoresist pattern is formed on the uppermost layer by a photolithography technique. The photoresist pattern serves as a mask pattern for forming via holes, in which openings are formed on regions where via holes are to be formed. Thereafter, the multilayer structure having the low dielectric film, the insulating film and the like is etched by using the photoresist pattern as a mask to form via holes reaching the Cu layer. The photoresist pattern is removed, and a sacrifice layer containing an alkoxysilane material or the like is charged in the via holes.
Subsequently, another photoresist pattern (mask pattern) for forming a trench pattern is formed on the uppermost layer on the remaining multilayer structure, and the low dielectric film, the insulating film and the sacrifice layer are partially etched to a prescribed depth with the pattern as a mask, whereby trenches for wiring reaching the via holes are formed. The sacrifice layer remaining in the via holes is then removed and cleaned. After removing the photoresist pattern, Cu is charged in the via holes and the trenches by plating process or the like, so as to form a multilayer Cu wiring.
In the formation process by the dual damascene process, it is necessary that not only the sacrifice layer is completely removed and cleaned, but also damages on the low dielectric layer having openings exposed to the dual damascene structure are suppressed.
Upon removal of the sacrifice layer in the dual damascene process, a buffered hydrofluoric acid and the like have been used as a remover liquid (as shown, for example, U.S. Pat. No. 6,365,529 (column 8, lines 2 to 6) and U.S. Pat. No. 6,329,118 (column 7, lines 57 to 61)), but in the case where the remover liquid is used, there is such a problem that damages on the low dielectric layer cannot be sufficiently suppressed.
The following remover liquids are proposed as a quaternary ammonium remover liquid in the photolithography field, i.e., a remover liquid containing a mixture of a quaternary ammonium salt, dimethyl sulfoxide and water (in particular, a dimethyl sulfoxide solution (containing 1.5 mass % of water) containing 0.5 mass % of tetramethylammonium hydroxide) (as described in JP-A-8-301911 (paragraphs 0032 and 0043), a stripping composition containing a polar aprotic solvent, such as dimethyl sulfoxide and sulfolane, and an aggressive base, such as a quaternary ammonium hydroxide, (as described in JP-A-2001-324823), and a remover liquid containing dimethyl sulfoxide, an alcohol amine, water and quaternary ammonium hydroxide (as described in JP-A-7-28254). However, these are used for removing an organic film, such as a photoresist, but there is no disclosure on removal of a sacrifice layer and no suggestion on suppression of damages on a low dielectric layer, in the dual damascene process.